Because of the increasing cost of electrical energy during the past decade, efforts have been made to substitute initially costlier but more energy efficient lamp types in place of incandescent lamps. There have been proposed lamp units which comprise a compact fluorescent discharge lamp or tube coupled respectively in a detachable or non-detachable manner to a housing which contains the lamp operating circuitry. The lamp operating circuitry may consist of, for example, an inductive ballast or an electronic circuit, the latter of which transforms the AC input signal into a high frequency. These lamp units have a standardized base for instance of the screw-in or bayonet type which can be directly inserted into a standardized socket.
An example of a compact fluorescent discharge lamp adapted for coupling in a detachable manner to a housing containing the lamp starting and operating circuitry is shown, for example, in U.S. Pat. No. 4,862,035 (Cunliffe et al). In FIG. 1 of the Cunliffe et al patent there is illustrated an example of a commercially available compact fluorescent lamp comprising two adjacent U-shaped tubes connected together to form an assembly 10. A jointing connection 12 provides a communication between the two tubes so that a single folded arc discharge path is provided through the two U-shaped tubes, via the joint 12. Each of the U-shaped tubes is provided with a corresponding filament at each end of the arc discharge path, only one such filament 14 being illustrated in the drawing.
The double twin-tube bulb 10 in the Cunliffe et al patent is supported in a two-part base that is comprised of an upper base shell 20 and a lower base bottom 22. The double twin-tube bulb 10 is secured in the upper base shell 20 by means of an appropriate cement such as illustrated at 24 in FIG. 1. In order to withstand the high temperatures required to cure typical basing cements, the base shell 20 is often constructed from a thermoplastic polyester material.
Base bottom 22 supports pins 26 and 28 and contains the starter circuit which consists of a glow bottle starter switch 30 and capacitor 32. The base bottom 22 and the pins 26 and 28 are adapted to form a plug connection capable of being electrically connected to a base fitting (sometime referred to as a lamp holder or adapter) that incorporates the associated lamp operating circuitry and has the standardized base required for insertion into an electrical socket intended to receive a conventional incandescent lamp. A commercially available lamp holder suitable for receiving such a replaceable compact fluorescent lamp as described above is similar to that shown in FIG. 1 of U.S. Pat. No. 4,654,557 (Haraden). Since the discharge tube in a replaceable lamp unit is not cemented to the housing of the fitting, the housing can be constructed from a material which is less expensive than thermoplastic polyester.
An example of an integral compact fluorescent lamp unit wherein the discharge tube in not detachable from the housing containing the lamp starting and operating circuitry is discussed, for example, in French Publication No. 0346782. Reference is made to FIG. 6 wherein a discharge tube having two branches 6 and 7 is sealed by means of cement 18 to the interior of an intermediate element (i.e., housing) 9. A conventional screw base 10 is fastened to the intermediate element. In order to withstand the high temperatures required to cure a conventional basing cement, this intermediate element must be constructed from a material which can withstand the cement's curing temperature. This material may be the same as that typically used for the lamp base shell discussed above.
Equipment is presently being used by lamp manufacturers to produce replaceable compact fluorescent lamps similar to those illustrated in FIG. 1 of the Cunliffe et al patent. In the process, an inventory of partially assembled lamps, consisting of discharge tubes cemented to upper base shells but not including the starting circuitry and lower base bottoms, may exist.
To be able to produce an integral compact fluorescent lamp unit, it is desirable from a manufacturing standpoint to be able to use as much of the previously available manufacturing equipment as possible as well as being able to use these partially assembled discharge tubes. Moreover, it is desirable to be able to manufacture an integral compact fluorescent unit wherein the unit housing, which may contain the lamp starting and operating circuitry, can be produced from a less expensive material.